Substation telephone circuit



Aug. 24, 1937. HL 2,091,115

SUBSTATION TELEPHONE CIRCUIT Filed June 15, 1935 l COIN T\C) Jw/r l/aa/f cause-r nsi H 4 M i u nsa INVENTOR.

HINRICH DOHLE ATTORNEY.

Patented Aug. 24, 1937 SUBSTATION TELEPHONE CIRCUIT Hinrich Dohle,-Haselhorst, Germany, assignor-tq Telephon-Apparat Fabrik E. Z'wietusch Company, Berlin, Germany Application June 15,

and

1935, Serial No. 26,723

In Germany June 29, 1934 Claims.

This invention relates to automatic substation telephone circuits in which it is necessary to deposit a coin to remove a short circuit from around the impulsing springs of a calling device in order 5 to complete a telephone connection or in which it is necessary to deposit a coin only on certain restricted connections.

It is common practice in some systems to have normally closed coin controlled springs close a 0 short circuit around the impulsing springs in order to render the impulsing springs inefiective until a coin is deposited to open the coin controlled springs and which coin is then collected by movement of the switchhook in response to the replacement of the receiver. In this type of system the deposited coin operates the coin controlled springs to open the short circuit from around the impulsing springs thereby enabling the subscriber to set up an automatic connection.

British Patent 198,131 shows coin controlled springs which normally short-circuit the impulsing springs and which springs are opened by a deposited coin to remove the short circuit and enable the subscriber to dial up a connection. In

this type of system wherein the replacement of the receiver collects the deposited coin and recloses the normally closed coin controlled springs, it is possible to release the first connection and establish'additional connections without depositgoing any further coins for such additional calls.

For example, in order to complete a second connection without depositing another coin the subscriber moves the dial off normal to open the impulsing springs thereby opening the station loop topermit release of the first connection.

After release of this first connection the subscriber may dial up the second connection since the switchhook has not been operated to collect the coin and close the short circuit around the 40 impulse springs.

It is well known that telephone stations which are not allowed to make all types of connections or in which the normally blocked connections can only be obtained after paying a certain fee, are

equipped with special blocking contacts controlled from the dial or calling device. These blocking contacts become operative on the dialling or selection of a particular blocked number, that is, one to which the station is denied access, and

are restored to the rest position by replacing the receiver. Patent 1,691,575, issued Nov. 13, 1928 to W. Kruse shows such an arrangement. In such stations there exists the possibility of deceit in that the connection may be released not by replacing the receiver but by allowing the dial to run back slowly. In this way the restoration of the blocking contacts is avoided so that on reseizing the selector switch the blocking contacts are in the displaced position.

The object of the present invention is to provide a subscribers paystation circuit which prevents the subscriber from releasing an established connection by interfering with the normal operation of the calling device and forcibly holding open the calling device impulse springs.

In order to exclude this possible deceit, many diverse arrangements have already been proposed. For example, the dial may be equipped with a special auxiliary contact dependent on the speed at which the dial runs back. This, however,-involves a special construction.

Another known method for preventing the possibility of the deceit mentioned, is to include in the station loop circuit a delayed release relay by which a contact is placed in the loop circuit and in parallel with an auxiliary contact which is controlled by the dial and which opens on the first actuation of thedial. On normal runningback of the dial the relay remains energized due to its delayed release and thus maintains the loop circuit closed. If, however, the motion of the dial is forcibly impeded, then there is a slower interruption of the exchange loop and the contact of the auxiliary relay opens so that the exchange loop remains broken as the auxiliary contact atthe dial is already open. To be able to produce a new connection and therefore pay another fee, the caller must replace the receiver in order to restore to the rest position the aux-- iliary contact controlled by the dial and to reclose the exchange loop.

The present invention also makesuse of a controlled auxiliary relay in the loopcircuit. Instead, however, of including the contact of this auxiliary relay in the exchange loop, according to the invention this contact is connected between the a and 2) lines in series with the dial off normal contact. This measure affords the advantage in comparison with the known arrangement because an entirely normal dial can be. used whereas in the known arrangement the dial must be equipped with a special auxiliary contact which becomes operative on the first actuation of the dial and is held in this position until the receiver is replaced.

One embodiment of the invention is shown in the drawing.

M is the microphone, F the receiver, nsi is the dial impulse contact, 0 the normally closed coin controlled springs, nsa the dial off normal contact, and HU the switch hook contact.

The mode of operation of the arrangement is as follows:

5 On removing the receiver the exchange loop is completed and relay R energizes over a circuit including the normally closed coin controlled springs c which normally short circuit the impulse springs nsz. If new the subscriber attempts to set up a connection without first depositing a coin the impulse springs nsi are ineffective since the normally closed coin controlled springs 0 short circuit the impulse springs mi. The subscriber now deposits a coin to open the normally closed coin controlled springs and remove the short circuit from around the impulse springs nsi to render these springs effective to set up the desired connection. When the dial is operated the contact nsa closes. If the dial runs back normally relay R remains energized since the interruption at contact nsz' does not succeed in causing the slow-acting relay R to deenergize. If, however, with the purpose of fraudulently releasing the connection contact nsi is held open for a longer time, relay R releases before the connection is released and at its contacts r places a shunt around contact nsi. The exchange loop is therefore reclosed before the connection is released, because the dial is still in the working position and contact me is closed so that the exchange loop is now maintained over: a, r, nsa, b,- and the connection is not released.

With this circuit arrangement the possibility of releasing the connection thus only occurs when on replacing the receiver, contact EU is opened.

This same circuit arrangement may be included in the restricted type of service shown in the aforementioned Patent 1,691,575 by including relay R, in the loop circuit and connecting the contact r and the dial off normal springs in series across the two line conductors. This circuit arrangement then prevents the release of the connection by forcibly retarding the calling de- L vice for this type of system over a circuit including contact 1' and the closed dial off normal contacts in bridge of the two line conductors. There fore, before a second restricted call can be made it is necessary to operate the switchhook, collect the deposited coin, and deposit a new coin.

Having described the invention, what is considered to be new and is desired to be protected by Letters Patent will be set forth in the following claims.

What is claimed is:

1. In an automatic substation telephone circuit, means for preventing the release of the connection when the calling device is forcibly retarded in restoring to normal, said means coma prising a relay energized during the normal operation of the calling device and deenergized when the calling device is slowly restored, and

vmeans controlled by said relay for placing a bridge across the telephone circuit while said calling device is still in its operated position.

2. In an automatic substation telephone circuit in which the subscriber by forcibly retarding the operation of the calling device is prevented from releasing the established connection, a slow acting relay in the substation circuit energized over the substation loop and held energized by the normal actuation of the calling device contacts controlled by said relay included in a bridge circuit of said telephone circuit, said relay maintaining said bridge circuit open as long as said calling device is operating normally, but closing said bridge circuit when said calling device is forcibly retarded in its operation.

3. In an automatic substation telephone circuit, a slow acting relay energized over the substation loop and held energized by the normal actuation of the substation calling device, normally closed contacts controlled by said relay and included in a bridge circuit of said telephone circuit, said relay restored to close said bridge circuit in response to said calling device being forcibly retarded in its operation, and a pair of contacts in said bridge circuit controlled by the calling device to close a further point in the bridge circuit as long as said calling device is in operating position.

4. In an automatic substation telephone circuit, a calling device, a slow acting relay operated over the substation loop and maintained operated by the normal actuation of said calling device, a bridge circuit across said telephone circuit, normally closed contacts controlled by said relay for opening a point in said bridge circuit, normally open contacts controlled by said calling device for closing a point in said bridge circuit, both of said contacts maintaining saidbridge circuit across said telephone circuit closed when the normal operation of said calling device is interfered with.

5. In an automatic substation telephone circuit, a bridge circuit across said telephone circuit, a calling device controlling a set of contacts in said bridge, a relay energized over the substation loop and controlled by said calling device, aset of contacts on said relay included in said bridge circuit, the normal operation of said calling device closing its contacts in the bridge circuit and also maintaining said slow relay energized to maintain its contacts open in the bridge circuit, said slow relay restored to close its contacts and the bridge circuit in response to said calling device being forcibly retarded or slowed down in its normal speed of operation.

HINRICH DOHLE. 

